The invention relates to a process for injection molding objects including at least two different layers. The outer layer is produced from a liquid enamel, which is injected by at least one enamel-injection apparatus through at least one enamel-injection die. A melted plastic material is introduced by an injection unit through a plastic-injection die into the cavity of an injection molding tool, also known as an injection molding form.
A similar process is disclosed in DE-OS 24 61 925. Enameled plastic molded bodies are produced by first injection molding the actual injection molded part of plastic material. Then, one side of the molded body is coated with enamel. For this purpose, the injection molding tool is opened by a certain amount, and liquid enamel is injected into the resulting cavity by an enamel-injection apparatus. By closing the tool, the enamel is distributed on this side of the molded body. The same procedure is repeated for the other side of the molded body.
Another process for producing enamel-coated injection molded parts is taught in DE 36 42 138 A1. Before the plastic material is introduced, the mold-forming surfaces of the injection molding tool or form are sprayed with enamel. Spray heads, integrated into the form, introduce the enamel before injection of the melt.
Finally, a similar process is known from the P 43 40 990, which is directed to a method for producing a plastic object of two different layers. The outer layer of the object is enamel, which is applied in a heated liquid state. The enamel is first placed, in the form of granulate, into a plasticising unit. Under the action of the kneading motion of an extruder screw and heat from heating elements, which are disposed about the extruder screw cylinder, the enamel granulate is plasticised and liquified. Through an injection molding die, it reaches the cavity of the injection molding form together with the plasticised plastic melt. An appropriately designed die here achieves the result that the enamel surrounds the plastic melt in the cavity of the injection molding form. It is also possible for one or more layers of enamel to be injected first into the cavity of the form, followed by the plastic in the liquid state. The molded parts thus receive a two- or multi-layered structure, such that the enamel layers completely surround the plastic material.